Various geodetic surveying apparatuses have been known since ancient times for surveying one or more target points. In this case, as a standard, spatial data, distance and direction, or angle from a measuring apparatus to the target point to be surveyed are recorded. In particular, the absolute position of the measuring apparatus is acquired together with possibly existing reference points.
Widely known examples of such geodetic surveying apparatuses comprise theodolites, tachymeters or total stations, which are also referred to as electronic tachymeters or computer tachymeters. A geodetic surveying instrument of the prior art is described, for example, in the publication document EP 1 686 350. Such apparatuses have electro sensor angle and distance measurement functions, which allow determination of direction and distance to a selected target. The angle and distance quantities are in this case determined in the internal reference system of the apparatus and, for an absolute position determination, may possibly also need to be correlated with an external reference system.
In many geodetic applications, points are surveyed by placing specially configured target objects at them. These usually consist of a pole having a targetable marking or a reflector for defining the measurement distance, or the measurement point. Using a central geodetic surveying apparatus, even a relatively large number of target objects can therefore be surveyed, although this requires that they be identified. In such surveying tasks, in order to control the measurement process and establish or register measurement parameters, various data, instructions, words and other information need to be transmitted between the target object—in particular a handholdable data acquisition apparatus at the target object—and the central measuring apparatus. Examples of such data are the identification of the target object, inclination of the pole, height of the reflector above ground, reflector constants or measurement values such as temperature or air pressure.
Modern total stations have microprocessors for the digital post-processing and storage of acquired measurement data. The apparatuses are generally produced in a compact and integrated design, usually with coaxial distance and angle measurement elements as well as calculation, control and storage units integrated in an apparatus. Depending on the development level of the total station, means for motorizing the target optics, for reflectorless distance measurement, for automatic target search and tracking and for remote control of the entire apparatus are integrated. Total stations known from the prior art furthermore have a radio data interface for setting up a radio link to external peripheral components, for example to a data acquisition apparatus which, in particular, may be formed as a hand-holdable data logger, remote control unit, array processor, notebook, small computer or PDA. By means of the data interface, measurement data acquired and stored by the total station can be output to external post-processing, externally acquired measurement data can be read into the total station for storage and/or post-processing, remote control signals for remote control of the total station or of another external component, particularly in mobile field use, can be input or output, and control software can be transferred into the total station.
For sighting or targeting the target point to be surveyed, geodetic surveying apparatuses according to the generic type comprise, for example, a target telescope, for example an optical telescope, as a sighting device. The target telescope can generally be rotated about a vertical axis and about a horizontal tilt axis relative to a base of the measuring apparatus, so that the telescope can be oriented towards the point to be surveyed by swivelling and tilting. In addition to the optical viewing channel, modern apparatuses often have a camera integrated in the target telescope, and for example oriented coaxially or parallel, for acquiring an image, in which case the acquired image may in particular be represented as a live image on the display of the display/control unit and/or on a display of the peripheral apparatus used for the remote control—for example of the data logger or the remote control unit. The optics of the sighting device may in this case have a manual focus—for example an adjustment screw for changing the position of focusing optics—or an autofocus, the focal position being changed for example by servo motors. Automatic focusing devices for target telescopes of geodetic apparatuses are known, for example, from DE 197 107 22, DE 199 267 06 or DE 199 495 80.
Particularly, the sighting of a target reflector may in this case be carried out by means of a live image, which is displayed to the user in the display of the data logger or of the remote control unit, which is provided by a camera—for example arranged coaxially in the target telescope or with an orientation parallel to the target telescope—as the sighting device of the total station. Accordingly, the user can orientate the total station with the aid of the live image in accordance with the desired target identifiable in the live image.
EP 1 734 336 discloses a surveying system comprising a target unit, which has a reflector and an optical receiver and transmitter. It is in this case proposed to use the optical transmitter of the target unit inter alia to assist the automatic target search process. Thus, after reception of the search or measurement radiation, the target object can communicate its own identification, for example the reflector number or the reflector type, back to the surveying station with the aid of the transmitter of the target unit. The surveying station can therefore identify the target object found and be configured optimally with respect to the target object.
EP 1 573 271 discloses a target unit also having an optical transmitter, wherein—after reception of measurement radiation of a surveying apparatus—the target unit sends back an optical signal on which the target unit's own identity is modulated. A feature common to the aforementioned surveying systems from the prior art is that, optionally with the use of a camera, the target unit or a surveying pole provided with the target unit is sighted or observed by a stationary position determination unit, for example a total station.
For controlling the surveying system, the user is provided a control unit—either fixedly connected to the surveying apparatus or the target unit or embodied as a handholdable remote control unit. Such control units comprise input means and output means, particularly embodied as a display or touch screen, and data processing and storing means for processing and storing surveying data.
The user can have the surveying data be visualized on the display. If there is surveying data of more than one surveying task stored in the control unit, the surveying tasks may be shown in a list, e. g. sorted by a file name or a date, and the user can select the surveying task, the data of which he wants to be output by the device. If there is data of many surveying tasks stored, disadvantageously, it can become difficult and time-consuming for the user—especially in the field—to remember the correct file name related to the requested surveying data.